/*
 * %W% %E%
 *
 * Copyright (c) 2006, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package java.nio.channels;

import java.io.IOException;
import java.nio.channels.spi.*;


/**
 * A pair of channels that implements a unidirectional pipe.
 *
 * <p> A pipe consists of a pair of channels: A writable {@link
 * Pipe.SinkChannel </code>sink<code>} channel and a readable {@link
 * Pipe.SourceChannel </code>source<code>} channel.  Once some bytes are
 * written to the sink channel they can be read from source channel in exactly
 * the order in which they were written.
 *
 * <p> Whether or not a thread writing bytes to a pipe will block until another
 * thread reads those bytes, or some previously-written bytes, from the pipe is
 * system-dependent and therefore unspecified.  Many pipe implementations will
 * buffer up to a certain number of bytes between the sink and source channels,
 * but such buffering should not be assumed.  </p>
 *
 *
 * @author Mark Reinhold
 * @author JSR-51 Expert Group
 * @version %I%, %E%
 * @since 1.4
 */

public abstract class Pipe {

    /**
     * A channel representing the readable end of a {@link Pipe}.  </p>
     *
     * @since 1.4
     */
    public static abstract class SourceChannel
	extends AbstractSelectableChannel
	implements ReadableByteChannel, ScatteringByteChannel
    {
	/**
	 * Constructs a new instance of this class.
	 */
	protected SourceChannel(SelectorProvider provider) {
	    super(provider);
	}

	/**
	 * Returns an operation set identifying this channel's supported
	 * operations.
	 *
	 * <p> Pipe-source channels only support reading, so this method
	 * returns {@link SelectionKey#OP_READ}.  </p>
	 *
	 * @return  The valid-operation set
	 */
	public final int validOps() {
	    return SelectionKey.OP_READ;
	}

    }

    /**
     * A channel representing the writable end of a {@link Pipe}.  </p>
     *
     * @since 1.4
     */
    public static abstract class SinkChannel
	extends AbstractSelectableChannel
	implements WritableByteChannel, GatheringByteChannel
    {
	/**
	 * Initializes a new instance of this class.
	 */
	protected SinkChannel(SelectorProvider provider) {
	    super(provider);
	}

	/**
	 * Returns an operation set identifying this channel's supported
	 * operations.
	 *
	 * <p> Pipe-sink channels only support writing, so this method returns
	 * {@link SelectionKey#OP_WRITE}.  </p>
	 *
	 * @return  The valid-operation set
	 */
	public final int validOps() {
	    return SelectionKey.OP_WRITE;
	}

    }

    /**
     * Initializes a new instance of this class.
     */
    protected Pipe() { }

    /**
     * Returns this pipe's source channel.  </p>
     *
     * @return  This pipe's source channel
     */
    public abstract SourceChannel source();

    /**
     * Returns this pipe's sink channel.  </p>
     *
     * @return  This pipe's sink channel
     */
    public abstract SinkChannel sink();

    /**
     * Opens a pipe.
     *
     * <p> The new pipe is created by invoking the {@link
     * java.nio.channels.spi.SelectorProvider#openPipe openPipe} method of the
     * system-wide default {@link java.nio.channels.spi.SelectorProvider}
     * object.  </p>
     *
     * @return  A new pipe
     *
     * @throws  IOException
     *          If an I/O error occurs
     */
    public static Pipe open() throws IOException {
	return SelectorProvider.provider().openPipe();
    }

}
